fix: anchor friday-voice gitignore to repo root

The unanchored pattern also swallowed compose/hf-pdocker-01/friday-voice/.
Only the top-level nested repo should be ignored.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.gitignore

@@ -23,4 +23,4 @@ Thumbs.db
 .superpowers/
 
 # Has its own repo: git.hobbs.farm/jeremy/friday-voice.git
-friday-voice/
+/friday-voice/